Common chemical may affect liver at low levels

NEW YORK (Reuters Health) - A new study suggests that a synthetic chemical that is ubiquitous in the environment and in people's blood may affect the liver -- though the significance for human health remains unclear.

The chemical in question is perfluorooctanoic acid (PFOA), which is used to make substances called fluoropolymers. Used in an array of manufacturing processes, fluoropolymers impart fire-resistance and water, stain and grease repellency to everything from carpets to cookware.

According to the U.S. Environmental Protection Agency (EPA), non-stick cookware and other consumer products coated with Teflon or similar trademark products are not manufactured with PFOA. However, some of these products may contain trace amounts of PFOA as impurities.

Research shows that PFOA persists in the environment and at low levels in most people's blood; exactly how it gets into the bloodstream is not clear, but contaminated water, dust and food are possibilities that researchers are currently investigating.

Also unclear are the potential human health effects of such everyday PFOA exposure. In lab animals, the chemicals have been shown to cause developmental problems and other adverse effects, including liver damage. But a number of human studies have found no evidence that PFOA exposure affects the liver.

In the new study, researchers in Taiwan used data from a U.S. government health study to look at the relationship between blood PFOA concentrations and liver enzyme levels. They found that among 2,200 U.S. adults, liver enzymes generally inched up in tandem with PFOA levels, particularly in obese individuals.

Liver enzymes are a marker of the organ's functioning, and significant elevations in the blood can indicate liver inflammation or other damage -- as seen in diseases like hepatitis and cirrhosis, or scarring of the liver.

The increases found in this study, however, were not enough to indicate liver damage, according to senior researcher Dr. Pau-Chung Chen, of the National Taiwan University College of Public Health in Taipei.

Instead, Chen told Reuters Health in an email, "This result particularly challenges other studies (suggesting) that there are no demonstrated liver effects, even among occupational workers, of PFOA exposures."

The findings, published in the American Journal of Gastroenterology, do not prove that PFOA in the blood directly affects the liver, according to Chen. "Nonetheless," the researcher added, "the associations between PFOA and liver enzymes raise concerns given their common presence in the general population."

Only 0.4 percent of adults in this study had undetectable PFOA levels. So it must be assumed that exposure to the chemical is "almost universal" in the general U.S. population, Chen noted.

Much more research is needed to understand the possible health implications of such low-level exposure. For its part, the EPA says it is continuing to investigate the potential risks of PFOA and related chemicals.

"However," the agency states on its Web site, "given the scientific uncertainties, EPA has not yet made a determination as to whether PFOA poses an unreasonable risk to the public, and there are no steps that EPA recommends that consumers take to reduce exposures to PFOA."

SOURCE: American Journal of Gastroenterology, online December 15, 2009.